Radio access schemes and radio networks (hereinafter referred to as a long term evolution (LTE) or an evolved universal terrestrial radio access (EUTRA)) of cellular mobile communication have been examined in the 3rd Generation Partnership Project (3GPP). In the LTE, a base station apparatus is referred to as an evolved NodeB (eNodeB) and a terminal apparatus is referred to as user equipment (UE). The LTE is a cellular communication system in which a plurality of areas covered by base station apparatuses are arranged in cell forms. A single base station apparatus may manage a plurality of cells.
The LTE may correspond to time division duplex (TDD). The LTE adopting a TDD scheme is referred to as a TD-LTE or LTE TDD. In the TDD, uplink and downlink signals are subjected to time division multiplexing.
The 3GPP have examined that traffic adaptation technologies and interference management and traffic adaptation technologies (DL-UL Interference Management and Traffic Adaptation) are applied to the TD-LTE. A traffic adaption technology is a technology for changing a ratio between an uplink resource and a downlink resource according to an uplink traffic and a downlink traffic. The traffic adaptation technology is also referred to as a dynamic TDD.
In NPL 1, a method of using a flexible subframe is suggested as a method of realizing traffic adaptation. A base station apparatus can receive an uplink signal or transmit a downlink signal in a flexible subframe. In NPL 1, a terminal apparatus regards a flexible subframe as a downlink subframe unless the terminal apparatus receives an indication to transmit an uplink signal in the flexible subframe from the base station apparatus.
NPL 1 discloses that an HARQ (hybrid automatic repeat request) timing with respect to a PDSCH (physical downlink shared channel) is determined based on newly introduced UL-DL configuration (uplink-downlink configuration) and an HARQ timing with respect to a physical uplink shared channel (PUSCH) is determined based on initial UL-DL configuration.
NPL 2 discloses that (a) UL/DL reference configuration is introduced and (b) some subframes can be scheduled for either of an uplink and a downlink via dynamic grant/assignment from a scheduler.